1. Field of the Invention
Implementations consistent with principles of the invention relate generally to data processing and, more particularly, to a label switched path (LSP) hierarchy for Multiprotocol Label Switching (MPLS) networks.
2. Description of Related Art
In a Multiprotocol Label Switching (MPLS) network, a signaling protocol may be used to set up a label switched path (LSP) in the MPLS network. MPLS may permit a network to direct a flow of datagrams along a predetermined path (e.g., a LSP) across the network. A “datagram(s)” may include any type or form of data, such as packet or non-packet data. As part of setting up the LSP, label switching routers (LSRs) included in the MPLS network may set up a label information base (LIB) which may map an incoming label from an input port of the LSR to an output port of the LSR and to a new label value. The LSRs may forward datagrams along links through the MPLS network based on labels attached to the datagrams that indicate which LSP to use. The label may be swapped to the new label at each router hop. In this way, a LSP may identify the specific path of nodes (e.g., routers) and links that the datagram takes through the MPLS network.
Generalized Multiprotocol Label Switching (GMPLS) may provide similar functionality as MPLS and some additional functionality. GMPLS may permit setting up LSPs in a packet switched network, and may generalize this notion to set up LSPs in non-packet switched networks traversing optical cross connects, synchronous optical network (SONET) cross connects, etc. Labels may be port numbers, lambdas, timeslots, etc. In order to support this flexibility, GMPLS extended the base signaling and routing protocols provided by MPLS.
GMPLS may allow a user to specify the start point, end point, and bandwidth required, and a GMPLS agent on the network elements may allocate the path through the network, provisioning the traffic path, setting up cross-connects, and allocating bandwidth from the paths for the user-requested service. The actual path that the traffic will take through the network is not specified by the user. However, many networks do not support GMPLS and only support MPLS.
Two kinds of LSPs that may be set up in a network running MPLS include control-driven LSPs and traffic engineered LSPs. A traffic engineered LSP through a network may be established using a signaling protocol such as RSVP-TE (resource reservation protocol with traffic engineering). RSVP may be used by either a host or routers to request or deliver specific qualities or services (QoS) for application data streams or flows. RSVP may define how applications place reservations and how they may relinquish the reserved resources once the need for them has ended.
A LSP hierarchy may permit nesting of one or more RSVP LSPs into another RSVP LSP called a Forwarding Adjacency LSP (FA-LSP). This may allow scaling of RSVP LSPs and reduce the control and forwarding plane state in the network. Unfortunately, a LSP hierarchy relies on GMPLS signaling and routing extensions that are not compatible with existing MPLS networks. Deploying a LSP hierarchy in a MPLS network would require that all routers in the network be upgraded to support GMPLS, a costly and time consuming network upgrade.